It would be cool to print out a black-and-white image on, say, a laser printer, which contained an unobtrusive embedded "watermark" or "barcode" that contained chroma information for the image --- rather like what the Apple II did to get NTSC color just by producing a pattern of 1's and 0's.
Then you could point, say, a cellphone camera at the image, and push a button, and see the image in color.
